1. Field of the Invention
The present invention relates to an engine and a straddle-type vehicle, and more particularly, to an engine with a pipe surrounding a spark plug and a straddle-type vehicle including such an engine.
2. Description of the Related Art
Straddle-type vehicles include motorcycles, for example. A motorcycle includes an engine. An engine is disclosed in JP 2009-133219 A, for example.
In the engine of JP 2009-133219 A, a plug tube is provided to surround the spark plug. The plug tube is held in a support cylindrical part. An O-ring is provided between the side wall of the plug tube and the support cylindrical part to provide a seal.
In JP 2009-133219 A, a concave groove is provided on the side wall of the plug tube, the groove having an opening at the outer periphery of the side wall. The O-ring is located in this concave groove. That is, according to JP 2009-133219 A, a concave groove in which the O-ring is to be positioned must be formed in the plug tube. As such, according to JP 2009-133219 A, a complicated arrangement for providing a seal between the side wall of the plug tube and the support cylindrical part must be provided.